During traditional operations involving the blood circulatory system such as open-heart surgery, a patent's blood is typically removed from the body, oxygenated, and then returned to the body under pressure. Typically, blood is returned from this extracorporeal circuit to the patient's aorta through an aortic cannula. The aorta is a vessel which experiences high internal fluid pressures during a normal heart operation, therefore it is desired to minimize any trauma suffered by the aorta during these operations such as incisions. The challenge is to design an aortic cannula with the smallest diameter tip to minimize the necessary incision in the aorta, but will accommodate the necessary fluid flow rates without damaging the patient's blood or aorta.
Another factor which challenges the designers of aortic cannulas is avoiding concentrated, high velocity fluid flow from the tip of the cannula into the aorta commonly known as a "jet blast" effect. Many patients having this type of surgery already have atheromatous material and/or adherent thromba within the aorta. Directing a blast or jet of blood against the wall of the aorta could easily dislodge small pieces of these materials from the aorta causing strokes or blood clots.
The challenge at hand is to design an aortic cannula, and specifically the distal tip of the cannula to accommodate the necessary volume of fluid flow while simultaneously minimizing the impact on the aorta as a result of the diameter of the tip and the avoidance of any jet blast effect on the interior wall of the aorta. Other cannula designs are seen in U.S. Pat. Nos. 5,616,137 to Lindsay, 5,643,226 to Cosgrove, et al., 5,084,033 to O'Neill, et al., and 5,330,433 to Fonger, et al.